The present invention relates generally to data processing systems and methods that analyze data resulting from biological and/or chemical reactions exhibiting amplification, such as a polymerase chain reaction (PCR).
Many experimental processes exhibit amplification of a quantity. For example, in PCR, the quantity may correspond to the number of parts of a DNA strand that have been replicated, which dramatically increases during an amplification stage that is exhibited in an amplification region of a PCR data plot. PCR data is typically described by a region showing a linear drifting baseline, which is a precursor to exponential growth in the amplification region. As the consumables are exhausted, the curve turns over and asymptotes. Other experimental processes exhibiting amplification include bacterial growth processes.
The quantity of the experimental process is detected from an experimental device via a data signal. For example, the data can be collected by imaging different excitation wavelengths and emission wavelengths from one or more reactions occurring in respective wells or tubes. The data signal contains data points that are analyzed to determine information about the amplification. The collected data is then typically stored for future use.
One example of an analysis that might be conducted using PCR data is known as baselining. The baseline represents noise or instrument-specific levels in the data, not amplification. In order to better analyze the amplification region of the data, it is often desirable to remove the linear drifting baseline from the data signal. Such baselining can help to determine the level of actual amplification above the baseline. For certain types of analysis, this allows comparison between the amplification levels of different curves, since the baselines can vary on a per-curve basis. An example of baselining can be found in US Patent Publication 2006/0269947, incorporated by reference for all purposes.
Another analysis often conducted using PCR data is to calculate some quantification, in either absolute or relative terms, of a specific target molecule in the reaction. This can be accomplished by designating a target signal threshold that corresponds to a reference threshold. The number of cycles required to reach this target threshold is then referred to as the Ct value. Previous methods for determining the Ct value of a reaction are often limited, for example, by the accuracy of the modeling of the raw data or noise in the raw data.
Although methods exist for these and other types of analysis, data collected from amplification systems often includes significant noise and other variable aspects, which can hinder an efficient and accurate determination of characteristics of a reaction. Accordingly, new methods for analyzing amplification curves are desired.